Luminaires with automated and remotely controllable functionality are well known in the entertainment and architectural lighting markets. Such products are commonly used in theatres, television studios, concerts, theme parks, night clubs, and other venues. A typical product will commonly provide control over the pan and tilt functions of the luminaire allowing the operator to control the direction the luminaire is pointing and thus the position of the light beam on the stage or in the studio. Typically this position control is done via control of the luminaire's position in two orthogonal rotational axes usually referred to as pan and tilt. Many products provide control over other parameters such as the intensity, color, focus, beam size, beam shape, and beam pattern. The beam pattern is often provided by a stencil or slide called a gobo which may be a steel, aluminum, or etched glass pattern. The products manufactured by Robe Show Lighting such as the Robin MMX Spot are typical of the art.
The optical systems of such automated luminaires may be designed such that a very narrow output beam is produced so that the units may be used with long throws or for almost parallel light laser like effects. These optics are often called ‘Beam’ optics. To form this narrow beam with the large light sources in the prior art, the output lens either needed to be very large with a large separation between the lens and the gobos or of a short focal length and much closer to the gobos. It is problematic to use a large separation with a large lens as such an arrangement makes the luminaire large and unwieldy, and makes automation of the pan and tilt movement difficult. Thus, the normal solution is a closer and smaller lens with a short focal length. Alternatively, the thick heavy front lens may be replaced with a Fresnel lens where the same focal length is achieved with a much lighter molded glass lens using multiple circumferential facets. Fresnel lenses are well known in the art and can provide a good match to the focal length of an equivalent plano-convex lens, however the image projected by such a lens is typically soft edged and fuzzy and not a sharp image as may be desired when projecting gobos or patterns.
FIG. 1 illustrates a multiparameter automated luminaire system 10. These systems commonly include a plurality of multiparameter automated luminaires 12 which typically each contain on-board a light source (not shown), light modulation devices, electric motors coupled to mechanical drive systems and control electronics (not shown). In addition to being connected to mains power either directly or through a power distribution system (not shown), each luminaire is connected in series or in parallel to data link 14 to one or more control desks 15. The luminaire system 10 is typically controlled by an operator through the control desk 15. Control of the automated luminaire 12 is effectuated by electromechanical devices within the automated luminaire 12 and electronic circuitry 13, including firmware and software within the control desk 15 and/or the automated luminaire 12. In many of the figures herein, important parts like electromechanical components such as motors and electronic circuitry, including software and firmware and some hardware, are not shown in order to simplify the drawings so as to teach how to practice the disclosures taught herein. Persons of skill in the art will recognize the need for these parts and should be able to readily fill in these parts.
FIG. 2 illustrates a prior art automated luminaire 12. A lamp 21 contains a light source 22 which emits light. The light is reflected and controlled by reflector 20 through a hot mirror 23, aperture or imaging gate 24, and optical devices 25, 27 which may include dichroic color filters, effects glass, and other optical devices well known in the art. Optical device 27 is the imaging component and may include gobos, rotating gobos, irises and framing shutters. The final output beam may be transmitted through focusing lens 28 and output lens 29. Output lens 29 may be a short focal length glass lens or equivalent Fresnel lens as described herein. Either optical device 27, focusing lens 28, or output lens 29 may be moved backwards and forwards along the optical axis to provide focus and/or beam angle adjustment for the imaging components. Hot mirror 23 is required to protect the optical devices 25 and 27 from high infra-red energy in the light beam and typically comprises a glass plate with a thin film dichroic coating designed to reflect long wavelength infra-red light radiation and only allow the shorter wavelength, visible, light to pass through and into the optical system.
More recently lamps 21 with extremely small light sources 22 have been developed. These often use a very short arc gap, of the order of 1 millimeter (mm), between two electrodes as the light producing means. These lamps are ideal for producing a very narrow beam as their source etendue is low, and the size of the lenses and optical systems to collimate the light from such a small source can be substantially reduced. However, the short arc and small light source coupled with the short focal length, and thus large light beam angles, of the reflector also tend to produce substantial amounts of unwanted and objectionable light spill which can escape between gobos or around the dimming shutters.
There is an increased need for an improved light control system for an automated luminaire utilizing a light source with an intense hotspot such that light spill around or between gobos and/or through the dimming shutter is reduced.